Hydraulic hammers can be attached to various machines such as excavators, backhoes, tool carriers, or other like machines for the purpose of milling stone, concrete, and other construction materials. The hydraulic hammer is mounted to a boom of the machine and connected to a hydraulic system. High pressure fluid in the hydraulic system is supplied to the hammer to drive a reciprocating piston in contact with a work tool, which in turn causes the work tool to reciprocate while in contact with the construction material.
In some applications, the hydraulic hammer may be equipped with an automatic shutoff that locks the piston in a downward position when the work tool is no longer in contact with the construction material (e.g., breaks through the construction material). The automatic shutoff stops the piston from continuing to drive the work tool further into broken construction material, without requiring operator intervention. As a result, the automatic shutoff prevents unnecessary machine movement and provides more accurate control.
An exemplary automatic shutoff device for a hydraulic hammer is disclosed in U.S. Pat. No. 4,281,587 (the '587 patent) that issued to Garcia-Crespo on Aug. 4, 1981. Specifically, the '587 patent discloses a hydraulic hammer having an automatic stopping device that allows the hammer to operate only when a tool is set against a workpiece, and stops operation of the hammer when the tool is taken away from the workpiece. The automatic stopping device includes a plunger that descends to its lowest operating position when the tool is not set against the workpiece. While in this position, an automatic stopping port is uncovered and pressurized fluid is allowed to bypass to a discharge line, thereby preventing upward movement of the plunger. To begin hammer operation again, the tool is set against the workpiece, causing enough upward force to move the plunger upward a distance to block the automatic stopping port, allowing the plunger to continue reciprocating.
Although the automatic stopping device of the '587 patent may be adequate for some applications, it may still be less than optimal. In particular, the automatic stopping device of the '587 patent requires significant machine force (e.g., weight) to press its work tool into the workpiece, such that it causes a reaction force that moves the plunger upward a distance to block the automatic stopping port. This force can typically only be provided by larger machines. Many smaller machines, however, do not have sufficient weight and/or power, and their hydraulic hammers are consequently stuck in the automatic stopping position. In these situations, an operator is required to manually switch off the automatic stopping device and/or discontinue use of the automatic stopping device, resulting in operating efficiencies and wasted downtime.
The disclosed system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.